Camera focuses just when zoomed in, but zoomed out it goes blurry

[Eric Simpson]

We're having a heck of a time with one of the three cameras in our studio. It's a Sony D50 and the settings on the offending camera and CCU are all the same as the ones that work perfectly. The symptoms are as follows:

The camera focuses just fine when at a narrow-angle shot, zoomed in all the way, etc. When I zoom out to get a medium shot of a person, they look very blurry and the image is darker than the rest of the cameras even though the f-stops, shutter, and all other settings are identical. I adjusted the lens flange focus (the focal length adjustment) and it makes no difference.

One thing I've noticed is that the Easy Focus mode temporarily takes this problem away, but it comes right back after the mode disappears after its 10-second running time...Is there something I'm overlooking that I'm missing here? This problem seemingly came out of nowhere, and I can't pinpoint where and when this issue started.

[Mark Bournes]

It sounds like your backfocus setting is off.

[Eric Simpson]

That's what I've been adjusting unfortunately. No matter what setting or how much I turn the back focus ring (which I adjusted according to the Sony manual), I can't get the image to look remotely clear when I'm at a wide-angle.

[Mark Bournes]

So you've adjusted the macro and the backfocus ring and still no luck?
Hmmm, you may need to send it in for repair?

[Andy Graham]

I had an XL1 fall from a crane once when the tripod failed and it resulted in what you've described. I sent it to canon and they replaced the mounts and recallibrated the lens but it was never the same after that. Sounds to me like maybe someones droped it and not said anything.

Andy.

[J. Stephen McDonald]

The suggestion that the lens mounts may have been broken or misaligned could be the cause of this. Does the focus look different from one side to the other? However, the fact that it has this problem only at a wide position, where the depth-of-focus is much greater, is puzzling. It may be that a lens element has been knocked loose or out of position, rather than the whole lens being crooked. It's also possible that the correct backfocus adjustment has not been found yet. This can be tricky and it may take an expert to reset everything in harmony. With both optics and electronics, often one thing has to be set first, before the other and then fine-tuned in a certain sequence.

Anytime numerous and sometimes unknown hands contact video equipment, mysterious disorders like this may appear and no one will be acknowledging responsibility. Some well-made lenses can withstand severe abuse and impacts-----and then sometimes not. I hope the solution here is just a matter of adjustments and not major surgery.

I twisted too hard on a telex lens on a small camcorder once and snapped one of the two lens mounts internally. It showed a fuzzy focus on one side, but this was worse at full zoom. I was able to open it up and replace the flimsy mounts with much sturdier ones of my own making, and the problem never recurred.

[Eric Simpson]

"Does the focus look different from one side to the other?"

No, the blurriness is consistent from one side to the other, top to bottom as well.

The thing that's getting me is that the "EZ Focus" mode that I played with just to see if something was set wrong. This mode basically adjusts the aperature on the fly with one hit of the buttong to make focusing a little easier when the lighting conditions are less than ideal. It stays on for 10 seconds, then shuts itself off like it's supposed to. However, right before this mode turns off, the image looks perfect! Whatever adjustment that mode is making is a good one, but then it turns off and goes back to being out of focus.

To further complicate things, this problem has shifted from one camera to the other!! We were in the process of trying to narrow the problem down to the camera/CCU/cable, and to my surprise after shifting things around, diagnosing, then putting everything back to normal, the original offending camera looked fine! I thought, "Great! Problem solved." I then turned on the other two cameras, and I noticed that this problem is now present on another camera. It's not our switcher causing the problem, as I checked the monitor output on the CCUs, and the blurriness shows up there, too. How could this issue seemingly "hop" from one camera to the other? All of the hardware is in place *exactly* as it was when this problem first arose, the issue is just on another camera now...


I'm extra stumped.

[Andy Graham]

The only way I can see that happening is if you had the lenses off both cameras and somehow got them mixed up and put the offending one on another camera. If thats the case you now know that its the lens at fault, and if its not maybe you should try switching them. Label the dodgy one and move it around the other cameras.

Andy.

[Paul R Johnson]

I was going to suggest a lense swap too - there is no way that soft images that can be sharpened by use of the zoom can be electronic, so nothing at the end of a cable can be responsible for this. My best guess is as the others have said - somebody has dropped the lense! (or, the camera and you've jarred the prism assembly.

When you adjust the back focus ring, what is the visual effect? does it go totally out of focus, and sharp at bothe ends of the zoom.

Sudden thought - not sure which lense you have, but the macro ring hasn't slipped has it? This will really mess up the lense sharpness, if the macro element is slightly off the non-macro position - I've just tried this on a fujinon and it is possible to have the macro ring slightly engaged, and this does exactly what you are describing - including the inability of the back focus adjustment to cure it - I can have the macro setting looking off, but it isn't - a little prod and it snaps back.

[J. Stephen McDonald]

Eric, there can be dozens of adjustments and combinations of adjustments that can skew your focus like this. Going on the premise that something (or more than one thing) is out of adjustment, I'd keep on trying to find where you can change something to solve it. As suggested, some control could have been set wrong and it's been undetected. The Macro setting has temporarily befuzzled me on several cameras, until I finally realized it had been bumped into the wrong position.

I'd just set the lens and camera there and look at it and think about it for awhile. Maybe some brilliant solution will volunteer itself. I'd also pursue some more lens-swapping, since you have them available and come to a more definitive conclusion about just where the problem lies. Good Luck.

[Gary Chavez]

http://www.mediacollege.com/download...ackfocus01.psd

take this,
print this.
stand 15-20' away.
put camera on a tripod or flat surface.
zoom all the way in.
focus on the center.
you are there when it stops shimmering.
pull out gently, adjusting so you remain in focus.
push back in and you should still retain focus.
this will take several tries and some crying and cursing.
everyone should acquire this skill.
good luck